Injury Severity Score

Overview and Desktop Calculator

Karim Brohi, London, UK, March 10, 2007

Introduction

The Injury Severity Score (ISS) is an anatomical scoring system that provides an overall score for patients with multiple injuries. Each injury is assigned an Abbreviated Injury Scale (AIS) score, allocated to one of six body regions (Head, Face, Chest, Abdomen, Extremities (including Pelvis), External). Only the highest AIS score in each body region is used. The 3 most severely injured body regions have their score squared and added together to produce the ISS score.

An example of the ISS calculation is shown below:

Region

Injury
Description

AIS

Square
Top Three

Head & Neck

Cerebral Contusion

3

9

Face

No Injury

0

Chest

Flail Chest

4

16

Abdomen

Minor Contusion of LiverComplex Rupture Spleen

25

25

Extremity

Fractured femur

3

External

No Injury

0

Injury Severity Score:

50

The ISS takes values from 0 to 75. If an injury is assigned an AIS of 6 (maximal), the ISS score is automatically assigned to 75. The ISS correlates linearly with mortality, morbidity, hospital stay and other measures of severity.

It's weaknesses are that any error in AIS scoring increases the ISS error, many different injury patterns can yield the same ISS score and injuries to different body regions are not weighted. Also, as a full description of patient injuries is not known prior to full investigation & operation, the ISS (along with other anatomical scoring systems) is not useful as a triage tool.